The present invention relates to conveyors and more particularly to conveyors which are especially suited for use in a foundry.
Modern foundries produce many castings daily. For each individual casting a separate mold must be made. To facilitate production, these molds are made in assembly line fashion with conveyors interconnecting the various work stations on the production line.
In the layout of a foundry system, it is commonly necessary to connect two parallel conveyors so that an article, such as a mold, may be moved from one conveyor to the other. Another common necessity in the layout of a foundry system is to minimize the space necessary for the foundry system. The above prerequisites require a conveyor system which conveys the molds between the various fixed equipment which performs certain operations in the construction of the molds. In order to reduce the necessary space required by a foundry system, it is commonly necessary to transfer the mold between two conveyors.
There are known conveyors which can move articles in a number of different directions in a foundry. Some foundry conveyor systems have used cars which run on rails to interconnect parallel conveyors. Since the molds are made of ceramic materials, such as sand, it is inevitable that during the transport of the molds some sand will fall from the mold. In a railed conveyor system, the sand accumulates on the rails and causes abrasion of the wheels and the track. In addition, if the car is self-propelled, the deposits of sand on the rails may be thick enough to prevent good traction between the rails and the wheels. These difficulties have been overcome by using dirt shields and wipers to keep the wheels and track free of sand. However, the wipers and shields reduce reliability and increase maintenance costs since they themselves are prone to failure and require frequent maintenance. Furthermore, the expense of such conveyor cars and their associated equipment have been another disadvantage in their use in a foundry conveyor system.
Another known foundry conveyor system for transferring an article between two conveyors is described in Herbruggen, U.S. Pat. No. 2,918,711. A carriage which supports an article thereon is disclosed with a fluid actuated double acting piston-cylinder unit to move the article across rollers supporting the article onto the rollers of the carriage. The carriage, which is supported by rollers on another conveyor, is then moved to a second position where the article can be rolled off the carriage and onto another roller conveyor system by means of another double acting fluid actuated piston and cylinder unit. Accordingly, the direction of movement of the article is changed.
Other known transfer devices which use piston-cylinder units include transferring the article from a conveyor line to gravity rollers, from the gravity rollers to power rollers and from the power rollers again to gravity rollers.
It should be understood that the weight of the article, such as a mold, to be transferred in a foundry transfer system is extremely heavy and that it is desirable to design the equipment to transfer such an article in a most economical fashion. In order to move such heavy articles, the cost of piston-cylinder units and the like is extremely high due to the substantial forces that they are required to generate in performing the transfer function required. Also, the associated limit switches, valves, and fluid circuits required are extremely complex and require substantial costs to be expended in their construction. Furthermore, the synchronization of the piston-cylinder units in such transfer devices is difficult.
When such devices as powered rollers and cylinders are utilized in which a portion thereof comes in contact with the article to be transferred, substantial wear occurs therebetween. In the case of powered rollers, the bottom of the article is worn. In the case of cylinders, the side of the article is "peened" when the fluid cylinder comes into contact with the article and drives it from one conveyor system to the other.
In addition, such known devices require additional space for the positioning of the location of the transfer devices and therefore are further inefficient.
Furthermore, the rollers of such known devices become worn out due to sand from the molds entering the rollers' bearings. This sand deteriorates the bearings and accordingly necessitates the replacement of the worn rollers.
The present invention is the result of a unique mechanical and electrical combination which permits the transfer of an article from one conveyor to another at a minimum of cost, wear on the article, space required by the system, and allows for synchronization of the transfer of the article from one conveyor system to another.